Method for producing anisotropic film

ABSTRACT

A simple method for producing an anisotropic film, which does not require a light irradiation device having a special mechanism or an advanced alignment adjustment system, is provided. A film containing a photoreactive material is arranged on a polarizing element, and an anisotropy is provided to the film containing a photoreactive material by irradiating the film with light through the polarizing element. With this method, an anisotropic film can be formed on the polarizing element.

TECHNICAL FIELD

The present invention relates to a method for producing an anisotropicfilm.

BACKGROUND ART

Conventional methods for producing anisotropic films include, forexample, a method of stretching a polymer film (uniaxially/biaxially),or a method of rubbing a film of polyimide, polyvinyl or the like.However, in the former method of stretching, it is difficult to controlthe condition for obtaining a desired anisotropy, and this may degradeaccuracy in the anisotropy of the thus obtained film. In the lattertreatment, rubbing may cause electrification in the film and generatedust.

For solving the above-mentioned problems, methods for producinganisotropic films, which do not require such stretching or rubbing, havebeen developed recently. Examples of the methods include a method forproducing an anisotropic film by irradiating a photocrosslinkablepolymer with polarized ultraviolet light so as to control a crosslinkagedirection of the polymer (see non-patent documents 1 and 2, forexample); a method for producing an anisotropic film by irradiating aphoto-decomposable polymer with polarized ultraviolet light so as tocontrol the direction of the decomposition of the intramolecularcoupling in the polymer (see non-patent document 3 and patent document1, for example); and a method for producing an anisotropic film byirradiating a photoisomerization polymer with polarized ultravioletlight so as to control the direction of isomerization of the polymer(see non-patent document 4, patent documents 2 and 3, for example).

However, any of these methods requires an ultraviolet irradiation devicewith a special mechanism for radiating polarized ultraviolet light. Inaddition to that, at the time of radiation of the polarized ultravioletlight, an advanced alignment adjustment for accurately adjusting thedirection of the entering light with respect to the polymer film isrequired as well.

Patent document 1: JP H09(1997)-230353 A

Patent document 2: JP 2990270

Patent document 3: JP 3113539

Non-patent document 1: M. Schadt et al., Jpn. J. Appl. Phys., 31, p.2155-p. 2164 (1992)

Non-patent document 2: M. Schadt, Nature, 381, p. 212, (1996)

Non-patent document 3: M. Nishikawa et al., Liquid Crystals, 26, p.575-580 (1992)

Non-patent document 4: Kunihiro Ichimura, “Applied Physics” vol. 62, No.10, p. 998 (1993)

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] FIG. 1 is a schematic cross-sectional view showing lightirradiation in one example of a manufacturing method according to thepresent invention.

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

An object of the present invention is to provide a method for enablingthe production of an anisotropic film in a simple manner without usingany special devices.

Means for Solving Problem

For achieving the object, a method for producing an anisotropic filmaccording to the present invention is characterized by arranging a filmcontaining a photoreactive material on a polarizing element andirradiating the film containing a photoreactive material with lightthrough the polarizing element, thereby providing an anisotropy to thefilm containing a photoreactive material.

Effect of the Invention

As mentioned above, the production method of the present inventionincludes arranging a photoreactive material film on a polarizing elementand irradiating the photoreactive material film with light through thepolarizing element. Therefore, unlike in a conventional technique, anyspecial devices are not required for the light irradiation device and ageneral-purpose light irradiation device can be used. Furthermore, sincethe polarizing element is irradiated with light, an advanced alignmentadjustment can be omitted, and anisotropy with a preferred axialaccuracy can be provided. In this manner, a special device is notrequired, and degradation of the axial accuracy can be prevented by useof the polarizing element, and thus a large-area anisotropic film can beproduced by using a large-area polarizing element. Moreover, sincetreatments such as stretching and rubbing are not required, unlike theconventional techniques, accuracy of the thus obtained anisotropy isimproved and furthermore, dust can be suppressed.

MODE FOR CARRYING OUT THE INVENTION

An example of the production method of the present invention will bedescribed below, though the present invention is not limited thereto.First, a photoreactive material film is arranged on a polarizingelement.

Though the polarizing element is not limited particularly, preferablyfor example, it can pass light having a wavelength in a range of 1 to780 nm. As mentioned below, for light to be radiated on a photoreactivematerial film, a preferable range is 1 to 780 nm, and more preferably, arange of 200 to 400 nm, since in many cases the photoreactive materialhas an absorbing wavelength to be absorbed in an ultraviolet range.

Though there is no particular limitation on the polarizing element, aprism polarizer, a polarizing filter, and a polarizer can be used, forexample. Examples of the prism polarizer include Glan-Thompsom prism,Glan-Laser prism, and Glan-Taylor prism, which include inorganiccrystals of calcite or the like. Among them, a Glan-Taylor prism free ofan adhesive layer is particularly preferred. For the polarizing filter,polarizing films or the like containing typical dichroic pigments can beused without any particular limitations.

For the polarizer, commonly-available products can be used without anyparticular limitations. It can be selected from films, prepared by beingdyed by adsorbing a dichroic material such as iodine or a dichroic dye,followed by crosslinking, stretching and drying according to a knownmethod, for example. Among them, films that can penetratelinearly-polarized light when natural light enters, more specifically,films having excellent light transmittance and polarization degree arepreferable. Examples of the polymer film in which the dichroic materialis to be adsorbed include hydrophilic polymer films such as polyvinylalcohol (PVA)-based films, partially-formalized PVA-based films,partially-saponified films based on ethylene-vinyl acetate copolymer,and cellulose-based films. Other than the above, a polyene alignmentfilm such as dehydrated PVA and dehydrochlorinated polyvinyl chloridecan be used, for example. Among them, the PVA-based film is preferable.An example of the polarizer is described in JP 2000-162432 A. Thepolarizer is an ultraviolet polarizer containing an acicular materialhaving an aspect ratio of at least 2 and a short diameter of 0.5 μm orless, the acicular material being dispersed in an ultraviolettransmitting film whose refractive index differs by at least 0.05 fromthat of the acicular material, while being aligned in a predetermineddirection. This polarizer can be prepared, for example, by biaxiallykneading 100 weight parts of polymethylpentene and 3 weight parts ofneedle titanium oxide being 0.1 μm at the short side and 10 μm at thelong side, which is then shaped to a film 300 μm in thickness at 270° C.by a T-die, and subsequently stretching 6 times its original length at190° C.

In the production method of the present invention, it is preferable thatthe polarizing element is used for the polarizer. Since a large-areapolarizing element is available, a large anisotropic film can beproduced and supplied as mentioned above.

The thickness of the polarizing element is not limited particularly, butit is for example in a range of 1 to 1000 μm, preferably in a range of 5to 500 μm, and more preferably in a range of 10 to 300 μm.

The photoreactive material film can be formed directly on the polarizingelement, or it can be arranged with interposition of additional layer(s)as mentioned below. When it is formed directly on the polarizingelement, for example, a solution or melt of a photoreactive material isapplied onto the polarizing element, which is then solidified.

For the photoreactive material, for example, any materials that canreact with light having a wavelength in a range of 1 to 780 nm can beused. Specific examples include: materials to be isomerized by light,such as azobenzene, stilbene, spiropyran, anthracene and derivativesthereof, materials that are dimerized/polymerized by light, such ascinnamate derivatives like polyvinyl cinnamate, coumarin cinnamates, andchalcone cinnamates; photo-decomposable materials such as polyimide andpolysiloxane; and a linear photopolymerization polymer or the like asrepresented by the following Formula (IV). These photoreactive materialscan be used alone or can be mixed with at least one of the othermaterials.

The photoreactive material film can contain further a liquid crystallinecompound as well as the photoreactive material. In this case, forexample, the liquid crystalline material can be added further to thesolution or melt of the photoreactive material. Examples of the liquidcrystalline compounds include liquid crystalline monomers, liquidcrystalline oligomers and liquid crystalline polymers. The liquidcrystalline monomers exhibit themselves liquid crystalline propertiesand examples thereof include azomethines, azoxys, cyanobiphenyls,cyanophenyl esters, benzoates, cyclohexane carboxylic acid phenylesters, cyanophenyl cyclohexanes, cyano-substituted phenylpyrimidines,alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolans, andalkenylcyclohexylbenzonitriles. The liquid crystalline oligomers are notlimited particularly, but an available example thereof is formed throughpolymerization of two to dozen or more of the above-mentioned liquidcrystalline monomers, where the oligomer itself exhibits a liquidcrystalline property. For the liquid crystalline polymers,conventionally-known polymers can be used without any particularlimitations, but an available example is formed by polymerizing theliquid crystalline monomers to a higher degree than in the case of theliquid crystalline oligomer, where the polymer itself exhibits a liquidcrystalline property. These liquid crystalline compounds can be usedalone or can be mixed with at least one of the other liquid crystallinecompounds. Examples of the mixture of two or more liquid crystallinecompounds are described in JP 2000-517605 A, and specific examples ofthe available mixtures are shown in the following Formulae (I), (II) and(III).

The photoreactive material film can contain the above-mentionedphotoreactive material and further a non-liquid crystalline polymer. Inthis case, for example, the non-liquid crystalline polymer can becontained further in the solution/melt of the photoreactive material.Alternatively, the solution/melt can contain a monomer, an oligomer orthe like for forming the non-liquid crystalline polymer by a subsequentpolymerization, crosslinking or the like. This non-liquid crystallinepolymer can be, for example, a non-liquid crystalline polymer formedfrom the above-mentioned liquid crystalline monomer and the liquidcrystalline oligomer. In general, monomers or oligomers to form thenon-liquid crystalline polymer exhibit a liquid crystalline property,but a polymer formed through polymerization of these monomers oroligomers exhibits not a liquid crystalline property but a non-liquidcrystalline property. The non-liquid crystalline polymer can be usedalone or it can be mixed with at least one of the other non-liquidcrystalline polymers.

The photoreactive material can be, for example, a liquid crystallinemonomer having a photoreactive site, a liquid crystalline oligomerhaving a photoreactive site, and a liquid crystalline polymer having aphotoreactive site. Examples of the liquid crystalline monomer, liquidcrystalline oligomer and liquid crystalline polymer are mentioned above.

The photoreactive site denotes a site that causes isomerization,decomposition, dimerization or polymerization due to light irradiation.Examples of such sites to cause isomerization due to light irradiationare azo, stilbene and the like. Examples of groups to cause dimerizationor polymerization due to light irradiation include a vinyl group, acinnamoyl group, a chalconyl group and the like. Examples of groups tocause decomposition due to light irradiation include imide groups andthe like. These photoreactive materials can be used alone, or pluralphotoreactive materials can be used in combination.

When using a solution of the photoreactive material in formation of thephotoreactive material film, the solution can be prepared by dissolvingthe photoreactive material in a solvent. The solvent can be selectedwithout any particular limitations as long as it can dissolve thephotoreactive material or the like, and the solvent can be determinedsuitably in accordance with the type of the photoreactive material.Specific examples thereof include halogenated hydrocarbons such aschloroform, dichloromethane, carbon tetrachloride, dichloroethane,tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzeneand orthodichlorobenzene; phenols such as phenol and parachlorophenol;aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzeneand 1,2-dimethoxybenzene; ketones such as acetone, methyl ethyl ketone,methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone andN-methyl-2-pyrrolidone; esters such as ethyl acetate and butyl acetate;alcohols such as t-butyl alcohol, glycerin, ethylene glycol, triethyleneglycol, ethylene glycol monomethyl ether, diethylene glycol dimethylether, propylene glycol, dipropylene glycol and2-methyl-2,4-pentanediol; amides such as dimethylformamide anddimethylacetamide; nitriles such as acetonitrile and butyronitrile;ethers such as diethyl ether, dibutyl ether and tetrahydrofuran; orcarbon disulfide, ethyl cellosolve or butyl cellosolve. These solventsmay be used alone or in combination of two or more. And the solvents arepreferred not to corrode the polarizing element.

The concentration of the photoreactive material in the photoreactivematerial solution is not limited particularly. For providing a viscositythat facilitates the coating, the photoreactive material is preferred tobe in a range of 0.1 to 30 wt % with respect to the solvent, preferably0.5 to 15 wt %, and more preferably 1 to 5 wt %. When the concentrationis 5 wt % or less, a viscosity for forming an extremely smooth coatingsurface can be obtained.

The above-mentioned photoreactive material solution or the melt(hereinafter, referred to as ‘photoreactive material solution’ forexample) can contain the liquid crystalline compound or the non-liquidcrystalline polymer as mentioned above.

The photoreactive material solution or the like can be blended furtherwith various additives such as a stabilizer, a plasticizer, metals orthe like as required.

When the photoreactive material includes the above-mentioned liquidcrystalline monomers or the liquid crystalline oligomers which will bepolymerized subsequently due to light irradiation, it is preferable thata photoinitiator is added further to the photoreactive material solutionor the like. Though there is no particular limitation about thephotoinitiator, for example, Irgacure907 (trade name), Irgacure369(trade name), Irgacure 184 (trade name), which are supplied by CibaSpecialties Chemicals, or the mixture, is preferred. The amount of thephotoinitiator to be added is not limited particularly as well.

Moreover, the photoreactive material solution or the like may containother resins, for example. Such resins can be, for example, resins forgeneral purpose use, engineering plastics, thermoplastic resins andthermosetting resins.

The resins for general purpose use can be, for example, polyethylene(PE), polypropylene (PP), polystyrene (PS), polymethyl methacrylate(PMMA), an ABS resin, an AS resin or the like. The engineering plasticscan be, for example, polyacetate (POM), polycarbonate (PC), polyamide(PA: nylon), polyethylene terephthalate (PET), polybutyleneterephthalate (PBT) or the like. The thermoplastic resins can be, forexample, polyphenylene sulfide (PPS), polyethersulfone (PES), polyketone(PK), polyimide (PI), polycyclohexanedimethanol terephthalate (PCT),polyarylate (PAR), liquid crystal polymers (LCP) or the like. Thethermosetting resins can be, for example, epoxy resins, phenolic resins,novolac resins or the like.

The method of coating the photoreactive material solution is not limitedparticularly but it is selected, for example, from spin coating, rollercoating, flow coating, die coating, blade coating, printing, dipcoating, flow-expanding, bar coating, gravure printing and extrusion.

The method for coating the melt of the photoreactive material is notlimited particularly as long as the melt can be coated on a surface ofthe polarizing element. The examples include casting, melt-extrusion orthe like.

The method of solidifying the photoreactive material solution is notlimited particularly, but it is selected from drying methods such asnatural drying and heat drying. The condition can be determined suitablywithout any particular limitations in accordance with, for example, thekinds of the materials of the polarizing element, the kinds of thephotoreactive materials, and the kinds of the solvent. In general, thetemperature for the process is preferred to be at a level that does notdegrade the polarizing element, and specifically, it is preferred to bein a range of 0 to 150° C., and more preferably, 20 to 60° C.

Though there is no particular limitation, the photoreactive materialfilm has a thickness in a range of 0.005 to 5 μm for example, preferablyin a range of 0.01 to 0.5 μm, and more preferably in a range of 0.05 μmto 0.1 μm.

The photoreactive material film can be formed directly on a polarizingelement as mentioned above. Alternatively, it can be arranged on thepolarizing element by sticking or the like. The photoreactive materialfilm can be prepared separately as mentioned above, or a commerciallyavailable product can be used.

When sticking the photoreactive material film onto the polarizingelement, for example, an adhesive or an adhesive agent can be used.Examples of the adhesive include polymer adhesives based on acrylicsubstance, vinyl alcohol, silicone, polyester, polyurethane, andpolyether; and rubber-based adhesives. The adhesive agents are prepared,for example, by including suitably as a base polymer, acrylic polymers,silicone-based polymers, polyester, polyurethane, polyether andsynthetic rubbers. It is preferable that the adhesive or the adhesiveagent has excellent optical transparency, and that will not hinderanisotropy to a photoreactive material film through light irradiation.

The photoreactive material film can be formed directly on the polarizingelement as mentioned above. Alternatively, it can be arranged on thepolarizing element through additional layer(s). When arranging thephotoreactive material film on the polarizing element through additionallayer(s), for example, the additional layer (for example, a protectivelayer as mentioned below) is formed on the polarizing element first, anda photoreactive material solution or the like is further coated thereonto form the photoreactive material film. Alternatively for example, itis possible to prepare the polarizing element, the additional layer andthe photoreactive material film respectively and they are adheredthrough the above-mentioned adhesive or an adhesive agent in a certainorder.

Though there is no particular limitation, the additional layerpreferably transmits a light beam that can pass the polarizing element.For example, the layer can be used for a protective layer for thepolarizing element. For the protective layer, conventionally-knowntransparent films can be used without any particular limitations. Forexample, the protective layer is preferred to have excellenttransparency, mechanical strength, thermal stability, moisture proof,isotropism and the like. Specific examples of materials for theprotective layers include cellulose-based resins such astriacetylcellulose (TAC), and transparent resins based on e.g.,polyester, polycarbonate, polyamide, polyimide, polyethersulfone,polysulfone, polystyrene, polynorbornene, polyolefin, acrylic, acetate,and polyvinyl alcohol. Resins that will be cured by heat or ultravioletrays, which are based on e.g., acrylic, urethane, acrylic urethane,epoxy, and silicone, can be used as well.

For the protective layer, for example, a polymer film that is describedin JP2001-343529 A (WO01/37007) can be used as well. The polymermaterial can be, for example, a thermoplastic resin whose side chain hassubstituted/unsubstituted imide groups, and a thermoplastic resin whoseside chain has substituted/unsubstituted phenyl groups and nitrilegroups. An example thereof is a resin composition containing alternatingcopolymer containing isobutene and N-methyl maleimide and anacrylonitrile-styrene copolymer. The polymer film can be prepared byextruding the resin composition, for example.

It is preferable that the protective layers are colorless, for example.Specifically, it is preferable that a retardation value (Rth) of thefilm in the thickness direction as represented by the following equationis in a range of −90 nm to +75 nm. More preferably, it is from −80 nm to+60 nm, and particularly preferably from −70 nm to +45 nm. When theretardation value is in the range of −90 nm to +75 nm, coloring (opticalcoloring) due to the protective film can be solved sufficiently. In theequation below, nx, ny and nz respectively denote refractive indices ofX-axis, Y-axis and Z-axis directions in the protective layer. The X-axisdenotes an axial direction presenting a maximum refractive index withinthe protective layer, and the Y-axis denotes an axial directionperpendicular to the X-axis within the plane. The Z-axis denotes athickness direction perpendicular to the X-axis and the Y-axis, and ‘d’denotes a thickness of the protective layer.Rth=[{(nx+ny)/2}−nz]·d

The protective layer further may have an optically-compensatingfunction. As such a protective layer having the optically-compensatingfunction, it is possible to use, for example, a known layer used forpreventing coloration caused by changes in a visible angle based onretardation in a liquid crystal cell or for widening a preferableviewing angle. Specific examples include various films obtained bystretching the above-described resins uniaxially or biaxially, analigned film of a liquid crystal polymer or the like, and a laminateobtained by providing an aligned layer of a liquid crystal polymer on atransparent base. Among the above, the aligned film of a liquid crystalpolymer is preferable because a wide viewing angle with excellentvisibility can be achieved. Particularly preferable is anoptically-compensating retardation plate obtained by supporting anoptically-compensating layer with the above-mentioned triacetylcellulosefilm or the like, where the optically-compensating layer is made of anincline-aligned layer of a discotic or nematic liquid crystal polymer.This optically-compensating retardation plate can be a commerciallyavailable product, for example, “WV film” (trade name) manufactured byFuji Photo Film Co., Ltd. Alternatively, the optically-compensatingretardation plate can be prepared by laminating two or more layers ofthe retardation film and the film support of triacetylcellulose film orthe like so as to control the optical properties such as retardation.

The protective layer can be formed suitably by a conventionally knownmethod such as a method of applying the above-mentioned various resinsonto a polarizing film or a method of laminating the resin film, theoptically-compensating retardation plate or the like on the polarizingfilm, or can be a commercially available product.

The thickness of the protective layer is not particularly limited. Forexample, the thickness is in the range not greater than 500 μm,preferably from 5 to 300 μm, and more preferably from 5 to 150 μm.

The protective layer further may be subjected to, for example, ahard-coating treatment, an antireflection treatment, treatments foranti-sticking, diffusion and anti-glare and the like. The hard-coatingtreatment aims at preventing scratches on the surfaces of the polarizingplate, and it is a treatment of, for example, providing a hardenedcoating film that is formed of a curable resin and has excellenthardness and smoothness onto a surface of the protective layer. Thecurable resin can be, for example, ultraviolet-curing resins of siliconebase, urethane base, acrylic, and epoxy base. The treatment can becarried out by a conventionally known method. The anti-stickingtreatment aims at preventing adjacent layers from sticking to eachother. The antireflection treatment aims at preventing reflection ofexternal light on the surface of the polarizing plate, and can becarried out by forming a conventionally known antireflection layer orthe like.

When external light is reflected on the surface of the polarizing plate,the reflection will inhibit visibility of light transmitted through thepolarizing plate. The anti-glare treatment aims at preventing suchinhibition of visibility. The anti-glare treatment can be carried out,for example, by providing microscopic asperities on a surface of theprotective layer by a conventionally known method. Such microscopicasperities can be provided, for example, by roughening the surface bysand-blasting or embossing, or by blending transparent fine particles inthe above-described resin when forming the protective layer.

The above-described transparent fine particles may be silica, alumina,titania, zirconia, stannic oxide, indium oxide, cadmium oxide, antimonyoxide or the like. Other than the above, inorganic fine particles havingan electrical conductivity or organic fine particles comprising, forexample, crosslinked or uncrosslinked polymer particles can be used aswell. The average particle diameter of the transparent fine particlesranges, for example, from 0.5 to 20 μm, though there is no particularlimitation. In general, a blend ratio of the transparent fine particlespreferably ranges from 2 to 70 parts by weight, and more preferablyranges from 5 to 50 parts by weight with respect to 100 parts by weightof the above-described transparent resin, though there is no particularlimitation.

The anti-glare layer in which the transparent fine particles are blendedcan be used as the protective layer itself or provided as a coatinglayer coated onto the protective layer surface. Furthermore, theanti-glare layer also can function as a diffusion layer to diffuse lighttransmitted through the polarizing plate and thereby widen the viewingangle (i.e., visually-compensating function, for example).

The antireflection layer, the anti-sticking layer, the diffusion layerand the anti-glare layer mentioned above can be laminated on thepolarizing element, as a sheet of optical layers comprising theselayers, separately from the protective layer.

Next, light is radiated on a photoreactive material film arranged on thepolarizing element, through the polarizing element.

An example of light irradiation is described below by using a crosssectional view of FIG. 1. As shown in FIG. 1, a photoreactive materialfilm 3 is arranged on a surface of a polarizing element 2. With a lightirradiation device 1, irradiated light 4 is radiated on thephotoreactive material film 3 from the polarizing element 2 side. Thelight emitted from the light irradiation device 1 passes through thepolarizing element 2 and forms polarized light 5. This polarized light 5is radiated partially on the photoreactive material film 3, so that thephotoreactive material film 4 changes the molecular structure at anirradiated part. In this manner, the molecular structure at theirradiated part becomes different from that at an unirradiated part, andthus the photoreactive material film 3 is provided with an anisotropy,thereby an anisotropic film is formed. This partial structural change isselected from isomerization, dimerization, polymerization,photo-decomposition or the like caused by light irradiation, inaccordance with the kind of the above-mentioned photoreactive materials.

The wavelength of the irradiated light is in a range of 1 to 780 nm, forexample, preferably in a range of 200 to 400 nm, and more preferably ina range of 290 to 400 nm. The wavelength of the irradiated light can beselected suitably in accordance with the kind of the photoreactivematerial. For example, in a case where the photoreactive material iscinnamate, a range of 250 to 330 nm is preferred; for an azo-basedmaterial, a range of 380 to 450 nm is preferred; and for polyimide, arange of 1 to 300 nm is preferred. There is no particular limitation forthe light irradiation device. For example, a commonly-used ultravioletirradiation device can be used for radiating at a wavelength of 200 to400 nm, and a commonly-used visible light irradiation device can be usedfor radiating light having a wavelength of 400 to 780 nm. It ispreferable that the radiated light will have a wavelength within a rangeof light that can pass through the polarizing element.

The radiated light is polarized after passing through the polarizingelement as mentioned above. In general, the types and degrees of thispolarization differ depending on the kinds of the polarizing elements.Therefore, it is possible to select the type and degree of polarizationin accordance with the kind of the polarizing element. In the presentinvention, due to polarization by the polarizing element, thephotoreactive material in the photoreactive material film is decomposed,isomerized, dimerized or polymerized for example, and thus the moleculeswill be aligned in a predetermined form. In this manner, the film isprovided with a refractive anisotropy.

In this manner, an anisotropic film is formed. The anisotropic film ofthe present invention can be used as a laminate with the polarizingelement for example. Alternatively, it can be peeled off from thepolarizing element and used alone.

Since the anisotropic film obtained by the production method of thepresent invention has an anisotropy for example, when a liquid crystallayer is formed on the film for example, the liquid crystal moleculescan be aligned. For this reason, the anisotropic film can be used alsofor an alignment film such as a liquid crystal alignment film.

Alternatively, the anisotropic film of the present invention can be usedas an optically anisotropic film. In particular, when theabove-mentioned liquid crystalline compound or the non-liquidcrystalline polymer are contained further in addition to thephotoreactive material and when the photoreactive material is a liquidcrystalline compound or a non-liquid crystalline polymer having aphotoreactive site, the film will exhibit an optical anisotropy. Thoughthe state of the optical anisotropy is not limited particularly, theoptical anisotropy will be, for example, optical uniaxiality or opticalbiaxiality in accordance with the kinds of the liquid crystallinecompound or the non-liquid crystalline polymer. The optical uniaxialityincludes, in general, a negative uniaxiality where principal refractiveindices nx and ny are substantially equal to each other and larger thannz (nx≈ny>nz), and a positive uniaxiality where a principal refractiveindices nx and ny are substantially equal to each other and smaller thannz (nx≈ny<nz). The optical biaxiality denotes that the principalrefractive indices nx, ny and nz in three directions are different fromeach other, and it includes, for example, a negative biaxiality(nx>ny>nz) and a positive biaxiality (nz>nx>ny). The above-noted nx, nyand nz denote refractive indices of X-axis, Y-axis and Z-axis directionsin the anisotropic film. The X-axis denotes an axial directionpresenting a maximum refractive index within the anisotropic film, theY-axis denotes an axial direction perpendicular to the X-axis within theplane, and the Z-axis denotes a thickness direction perpendicular to theX-axis and the Y-axis.

Next, the optical film of the present invention is characterized in thatit includes an anisotropic film of the present invention. When theanisotropic film of the present invention exhibits an optical anisotropyas mentioned above, an optical film including the anisotropic film isuseful for an optically-compensating film or a retardation plate.

The optical film of the present invention will not be limitedparticularly as long as it includes an anisotropic film of the presentinvention. Therefore, the anisotropic film of the present invention canbe applied alone. Alternatively, it can be laminated with a polarizingelement as mentioned above, or can include further additional opticalelement(s).

Conventionally-known various optical elements, which are used for imagedisplay devices such as liquid crystal displays, can be used for theadditional optical element as mentioned above without any particularlimitations. The examples include a polarizing plate, a reflector, asemitransparent reflector, and a brightness-enhancement film. Theseadditional optical elements can be used alone or at least two kinds ofoptical elements can be used together. Such an optical element can forma single layer or a laminate of at least two layers. For the opticalfilm further including additional optical element(s), for example, anintegrated polarizing plate having an optically-compensating function ispreferred. Such an integrated polarizing plate is suitably used forvarious image display devices. For example, it can be arranged on asurface of a liquid crystal cell.

Lamination of the anisotropic film of the present invention and anadditional optical element can be carried out by a conventionally knownprocess without any particular limitations. For example, an adhesiveagent, an adhesive and the like as mentioned above can be used, and thekind can be determined suitably in accordance with the materials or thelike of the respective components. The adhesives are made of polymersbased on acrylic substances, vinyl alcohol, silicone, polyester,polyurethane and polyether, and rubber-based adhesives, for example. Theadhesive can contain further a water-soluble crosslinking agent of avinyl alcohol-based polymer such as boric acid, borax, glutaraldehyde,melamine and oxalic acid. Such an adhesive agent or adhesive can realizeresistance to peeling under the influence of moisture or heat andexcellent light transmittance and polarization degree. Specifically,when the additional optical element is a PVA-based film, for example, aPVA-based adhesive is used preferably from aspects of stability in anadhesion treatment or the like. Such an adhesive or an adhesive agentcan be applied directly onto the surface of a polarizing element or aprotective layer. Alternatively, a layer of the adhesive or the adhesiveagent formed as a tape or a sheet can be arranged on the surface. Whensuch an adhesive or an adhesive agent is prepared as a solution, otheradditive(s) or catalyst(s) such as acid(s) can be blended as required.When applying such an adhesive, for example, other additive(s) orcatalyst(s) such as acid(s) can be blended in the adhesive solution.Though the thickness of the adhesive layer is not limited particularly,for example, it ranges from 1 nm to 500 nm, preferably from 10 nm to 300nm, and more preferably from 20 nm to 100 nm. These adhesives can beused, for example, by coating an aqueous solution of the adhesive onto asurface of the respective component and drying. In the aqueous solution,for example, other additive(s) or catalyst(s) such as acid(s) can beblended. Among them, for the adhesive, a PVA-based adhesive is preferredin light of the excellent adhesiveness to the PVA film.

Next, as an example of the optical film of the present invention, apolarizing plate with an anisotropic film (integrated polarizing plate)will be explained below. The integrated polarizing plate is formed bylaminating an anisotropic film of the present invention and a polarizingplate.

First, an example of a reflective polarizing plate or a semitransparentreflective polarizing plate will be described. The reflective polarizingplate is prepared by laminating further a reflector on a laminate of ananisotropic film of the present invention and a polarizing element(e.g., a polarizing plate), and the semitransparent reflectivepolarizing plate is prepared by laminating a semitransparent reflectoron a polarizing plate of the present invention.

For example, such a reflective polarizing plate is arranged on abackside of a liquid crystal cell in order to make a liquid crystaldisplay (reflective liquid crystal display) to reflect incident lightfrom a visible side (display side). The reflective polarizing plate hassome advantages, for example, assembling of light sources such as abacklight can be omitted, and the liquid crystal display can be thinnedfurther.

The reflective polarizing plate can be formed in any known manner suchas forming a reflector of metal or the like on one surface of apolarizing plate having a certain elastic modulus. More specifically,one example thereof is a reflective polarizing plate formed by mattingone surface (surface to be exposed) of a protective layer of thepolarizing plate as required, and providing the surface with a depositedfilm or a metal foil comprising a reflective metal such as aluminum.

An additional example of a reflective polarizing plate is prepared byforming, on a protective layer having a surface with microscopicasperities due to microparticles contained in various transparentresins, a reflector corresponding to the microscopic asperities. Thereflector having a microscopic asperity surface diffuses incident lightirregularly so that directivity and glare can be prevented andirregularity in color tones can be controlled. The reflector can beformed by attaching the metal foil or the metal deposited film directlyon an asperity surface of the transparent protective layer in anyconventional and appropriate methods including deposition and platingsuch as vacuum deposition, ion plating and sputtering.

As mentioned above, the reflector can be formed directly on a protectivelayer of a polarizing plate. Alternatively, the reflector can be used asa reflecting sheet formed by providing a reflecting layer onto anappropriate film similar to the transparent protective film. Since atypical reflecting layer of a reflector is made of a metal, it ispreferably used in a state such that the reflecting surface of thereflecting layer is covered with the film, a polarizing plate or thelike in order to prevent a reduction of the reflection rate due tooxidation, and furthermore, the initial reflection rate is maintainedfor a long period, and a separate formation of a protective layer isavoided.

A semitransparent polarizing plate is provided by replacing thereflector in the above-mentioned reflective polarizing plate by asemitransparent reflector, and it is exemplified by a half-mirror thatreflects and transmits light at the reflecting layer.

In general, such a semitransparent polarizing plate is arranged on abackside of a liquid crystal cell. In a liquid crystal display includingthe semitransparent polarizing plate, incident light from the visibleside (display side) is reflected to display an image when a liquidcrystal display is used in a relatively bright atmosphere, while in arelatively dark atmosphere, an image is displayed by using a built-inlight source such as a backlight on the backside of the semitransparentpolarizing plate. In other words, the semitransparent polarizing platecan be used to form a liquid crystal display that can save energy for alight source such as a backlight under a bright atmosphere, while abuilt-in light source can be used under a relatively dark atmosphere.

Next, as one example of an optical film of the present invention, apolarizing plate prepared by further laminating a brightness-enhancementfilm on an anisotropic film of the present invention and a polarizingelement (e.g., a polarizing plate) will be explained below.

A suitable example of the brightness-enhancement film is notparticularly limited, but it can be selected from a multilayer thin filmof a dielectric or a multilayer lamination of thin films with variedrefraction anisotropy that transmits linearly polarized light having apredetermined polarization axis while reflecting other light. Examplesof such a brightness-enhancement film include trade name: “D-BEF”manufactured by 3M Co. Also a cholesteric liquid crystal layer, morespecifically, an aligned film of a cholesteric liquid crystal polymer oran aligned liquid crystal layer fixed onto a supportive film base can beused as the brightness-enhancement film. Such a brightness-enhancementfilm reflects either clockwise or counterclockwise circularly polarizedlight while transmitting other light. Examples of such abrightness-enhancement film include trade name: “PCF 350” manufacturedby Nitto Denko Corporation; trade name: “Transmax” manufactured by Merckand Co., Inc.

The above-mentioned optical film of the present invention can be, forexample, an optical element formed by laminating an anisotropic film ofthe present invention and a polarizing element, and further at least twoadditional optical elements.

An optical member including a laminate of at least two optical elementscan be formed, for example, by a method of laminating layers separatelyin a certain order for manufacturing a liquid crystal display or thelike. However, efficiency in manufacturing a liquid crystal display canbe improved by using an optical member that has been laminatedpreviously because of its excellent stability in quality, assemblingoperability and the like. Any appropriate adhesives such as an adhesiveagent layer can be used for lamination.

Moreover, it is preferable that the above-mentioned optical film of thepresent invention further has an adhesive agent layer or an adhesivelayer so as to allow easier lamination onto the other members such as aliquid crystal cell. They can be arranged on one surface or bothsurfaces of the optical film. The material of the adhesive agent layeris not particularly limited but can be a conventionally known materialsuch as acrylic polymers. Further, the adhesive agent layer having a lowmoisture absorption coefficient and an excellent thermal resistance ispreferable, for example, from the aspects of prevention of foaming orpeeling caused by moisture absorption, prevention of degradation in theoptical properties and warping of a liquid crystal cell caused bydifference in thermal expansion coefficients, and formation of a liquidcrystal display with high quality and excellent durability. It is alsopossible to incorporate fine particles so as to form the adhesive agentlayer showing light-diffusion property. For the purpose of forming theadhesive agent layer on the surface of the optical film, a solution ormelt of a sticking material can be applied directly on a predeterminedsurface of the polarizing plate with anisotropic film by a developmentmethod such as flow-expansion and coating. Alternatively, an adhesiveagent layer can be formed on a separator, which will be described below,in the same manner and transferred to a predetermined surface of theoptical film. Such a layer can be formed on any surface of the opticalfilm. For example, it can be formed on an exposed surface of theanisotropic film.

When a surface of a layer of an adhesive agent or the like provided onthe optical film is exposed, preferably, the adhesive agent layer iscovered with a separator until the time the pressure-sensitive adhesivelayer is used so that contamination or the like will be prevented.Preferably, the separator has a peeling coat on a surface to be broughtinto a contact with a surface of the adhesive agent layer. The peelingcoat can be formed by applying onto the separator a peeling agent basedon silicone, long-chain alkyl, fluorine, molybdenum sulfide or the likeas required.

The adhesive agent layer or the like can be a monolayer or a laminate.The laminate can be a combination of monolayers different from eachother in type or in composition. The adhesive agent layers arranged onboth surfaces of the optical film can be the same or different from eachother in type or in composition. The thickness of the adhesive agentlayer can be determined appropriately depending on the constituents orthe like of the optical film. In general, the thickness of the adhesiveagent layer is 1 μm to 500 μm.

It is preferable that the adhesive agent layer is made of an adhesiveagent having excellent optical transparency and sticking characteristicssuch as wettability, cohesiveness, and adhesiveness. As a specificexample, the adhesive agent can be prepared appropriately based onpolymers such as an acrylic polymer, a silicone-based polymer,polyester, polyurethane, polyether, and synthetic rubber.

Sticking characteristics of the adhesive agent layer can be controlledappropriately in a known manner. For example, the degree ofcross-linkage and the molecular weight will be adjusted on the basis ofa composition, molecular weight, crosslinking type, a content of thecrosslinking functional group, and an amount of the blended crosslinkingagent of the base polymer of the adhesive agent layer.

The respective layers composing the optical film of the presentinvention can have ultraviolet absorption power as a result of treatmentwith an ultraviolet absorbent such as a salicylate-based compound, abenzophenone-based compound, a benzotriazole-based compound, acyanoacrylate-based compound, and a nickel complex salt-based compound.

As mentioned above, the optical films of the present invention can beused preferably for forming various devices such as liquid crystaldisplays. For example, an optical film of the present invention isarranged on at least one surface of a liquid crystal cell in order toform a liquid crystal panel used in a liquid crystal display of, e.g., atransmission type, a reflection type, or a transmission-reflection type.

The type of the liquid crystal cell for composing the liquid crystaldisplay can be selected arbitrarily, and examples thereof includevarious cells such as an active matrix driving type represented by athin film transistor, a simple matrix driving type represented by a TN(Twisted Nematic) cell and an STN (Super Twisted Nematic) cell, an OCB(Optically Compensated Birefringence) cell, a HAN (Hybrid AlignedNematic) cell, and a VA (Vertical Aligned) cell.

In general, the liquid crystal cell is composed of opposing liquidcrystal cell substrates and a liquid crystal injected into a spacebetween the substrates. The liquid crystal cell substrates can be madeof glass, plastics or the like without any particular limitations.Materials for the plastic substrates can be selected from conventionallyknown materials without any particular limitations.

When various optical members are arranged on both surfaces of a liquidcrystal cell, they can be the same or different types. Moreover, forforming a liquid crystal display, one or more layers of appropriatemembers such as a prism array sheet, a lens array sheet, an opticaldiffuser and a backlight can be arranged at proper positions.

The liquid crystal display of the present invention is not particularlylimited as long as it includes a liquid crystal panel having theabove-mentioned optical film of the present invention. When it includesa light source, preferably, the light source is a flat light sourceemitting polarized light for enabling effective use of light energy,though there is no particular limitation.

For an example of a liquid crystal panel of the present invention, thefollowing configuration can be referred to. For example, it has a liquidcrystal cell, an optical film of the present invention (e.g., a laminateof an anisotropic film and a polarizing element), a polarizer and aprotective layer, where the optical film is laminated on one surface ofthe liquid crystal cell, while the polarizer and the protective layerare laminated in this order on the other surface of the optical film.The liquid crystal cell has a configuration to hold a liquid crystalbetween two liquid crystal cell substrates. When the optical film is alaminate of an anisotropic film and a polarizing element as mentionedabove, though the arrangement is not limited particularly, for example,the anisotropic film side faces preferably the liquid crystal cell.

The liquid crystal display of the present invention can includeadditionally on the visible side of the optical film, for example, adiffusion plate, an anti-glare layer, an antireflection film, aprotective layer, and a protective plate. Alternatively, a compensatingretardation plate or the like can be arranged suitably between theliquid crystal cell and the polarizing plate in the liquid crystalpanel.

The optical film of the present invention can be used not only in theabove-described liquid crystal display but also in, for example,self-light-emitting displays such as an organic electroluminescence (EL)display, a plasma display (PD) and a FED (Field Emission Display). Whenit is used in a self-light-emitting flat display, for example, thein-plane retardation values And of the optical film of the presentinvention are set to λ/4 in order to obtain circularly polarized light,and thus it can be used for an antireflection filter.

The following is a specific description of an electroluminescence (EL)display comprising the optical film of the present invention. The ELdisplay of the present invention is a display having the optical film ofthe present invention, and can be either an organic EL display or aninorganic EL display.

In recent EL displays, for preventing reflection from an electrode in ablack state, use of an optical film such as a polarizer and a polarizingplate as well as a λ/4 plate is proposed. The optical film of thepresent invention is especially useful when linearly polarized light,circularly polarized light or elliptically polarized light is emittedfrom an EL layer. The optical film of the present invention isespecially useful when an oblique light beam is partially polarized evenin the case where natural light is emitted in a front direction.

Now, a typical organic EL display will be explained below. In general,such an organic EL display has a luminant (organic EL luminant) that isprepared by laminating a transparent electrode, an organic luminantlayer and a metal electrode in this order on a transparent substrate.Here, the organic ruminant layer is a laminate of various organic thinfilms. Examples thereof include various combinations such as a laminateof a hole injection layer made of a triphenylamine derivative or thelike and a ruminant layer made of a fluorescent organic solid such asanthracene; a laminate of the luminant layer and an electron injectionlayer made of a perylene derivative or the like; and a laminate of thehole injection layer, the ruminant layer and the electron injectionlayer.

In general, the organic EL display emits light according to thefollowing principle: a voltage is applied to the anode and the cathodeso as to inject holes and electrons into the organic ruminant layer,energy generated by the re-bonding of these holes and electrons excitesthe fluorescent substance, and the excited fluorescent substance emitslight when it returns to the basis state. The mechanism of there-bonding of these holes and electrons during the process is similar tothat of an ordinary diode. This implies that the current and the lightemitting intensity show a considerable nonlinearity accompanied with arectification with respect to the applied voltage.

It is required for the organic EL display that at least one of theelectrodes is transparent so as to obtain luminescence at the organicruminant layer. In general, a transparent electrode of a transparentconductive material such as indium tin oxide (ITO) is used for theanode. Use of substances having small impedance for the cathode iseffective for facilitating the electron injection and thereby raisingluminous efficiency, and in general, metal electrodes such as Mg—Ag andAl—Li can be used.

In an organic EL display configured as described above, it is preferablethat the organic luminant layer usually is made of a film that isextremely thin such as about 10 nm, so that the organic luminant layercan transmit substantially all light like the transparent electrode. Asa result, when the layer does not illuminate, a light beam entering fromthe surface of the transparent substrate and passing through thetransparent electrode and the organic luminant layer is reflected at themetal layer so that it comes out again to the surface of the transparentsubstrate. Thereby, the display surface of the organic EL display lookslike a mirror when viewed from exterior.

For example, an organic EL display of the present invention, whichincludes the organic EL luminant, has a transparent electrode on thesurface side of the organic ruminant layer, and a metal electrode on thebackside of the organic ruminant layer. In the organic El display, it ispreferable that an optical film of the present invention is arranged onthe surface of the transparent electrode, and furthermore, a λ/4 plateis arranged between the polarizing plate and an EL element. As describedabove, an organic EL display obtained by arranging an optical film ofthe present invention can suppress external reflection and improve thevisibility. It is further preferable that a retardation plate isarranged between the transparent electrode and the optical film.

For example, the optical film polarizes light which enters from outsideand is reflected by the metal electrode, and thus the polarization hasan effect that the mirror of the metal electrode cannot be viewed fromthe outside. Particularly, the mirror of the metal electrode can beblocked completely by forming the retardation plate with a quarterwavelength plate and adjusting an angle formed by the polarizationdirections of the retardation plate and the optical film (e.g., alaminate of an anisotropic film and a polarizing element) to be π/4.That is, the optical film transmits only the linearly polarized lightcomponent among the external light entering the organic EL display. Ingeneral, the linearly polarized light is changed into ellipticallypolarized light by the retardation plate. When the retardation plate isa quarter wavelength plate and when the angle is π/4, the light ischanged into circularly polarized light.

This circularly polarized light passes through, for example, thetransparent substrate, the transparent electrode, and the organic thinfilm. After being reflected by the metal electrode, the light passesagain through the organic thin film, the transparent electrode and thetransparent substrate, and turns into linearly polarized light at theretardation plate. Moreover, since the linearly polarized light crossesthe polarization direction of the optical film at a right angle, itcannot pass through the optical film. Consequently, as described above,the mirror of the metal electrode can be blocked completely.

The following is a further description of the present invention by wayof Examples and Comparative Examples. It should be noted that thepresent invention is not limited to these Examples alone.

EXAMPLE 1

Polyvinyl cinnamate (photoreactive material) was dissolved in acyclopentanone solvent to prepare a 5 wt % solution to be applied. Thispolyvinyl cinnamate solution was applied on one face of a Glan-Taylorprism (polarizing element) by spin coating. The thus coated film wasdried at 100° C. for 3 minutes so as to form a polyvinyl cinnamate film(photoreactive material film) 100 nm in thickness, thereby obtaining alaminate.

Next, the laminate was irradiated with light for 6 minutes with anultraviolet irradiation device using a high-pressure mercury lamp(illumination: 15 mW/cm²). The incidence angle of the radiated light wasadjusted to 90° with respect to the polarizing element. The integratedquantity of light after passing through the polarizing element was 1J/cm². Thereby, a light beam that had changed to polarized light afterpassing through the polarizing element was radiated on the photoreactivematerial film, and thus an anisotropic film was formed on the polarizingelement.

EXAMPLE 2

An anisotropic film was formed on a polarizing element in the samemanner as Example 1 except that stilbene was used for the photoreactivematerial.

EXAMPLE 3

A photoreactive material (trade name: LPPF301 manufactured by VanticoCo., Ltd.) was dissolved in a cyclopentanone solvent to prepare a 2 wt %solution to be applied. The solution was applied on one face of apolarizing filter (trade name: Ultraviolet Polarizer, manufactured byBolder Vision Optik) by spin coating. The thus coated film was dried at100° C. for 3 minutes so as to form a photoreactive material film 100 nmin thickness, thereby obtaining a laminate.

Next, the laminate was irradiated with light for 3 minutes with anultraviolet irradiation device using a high-pressure mercury lamp(illumination; 15 mW/cm²). The incidence angle of the radiated light wasadjusted to 90° with respect to the polarizing element. The integratedquantity of light after passing through the polarizing element was 0.5J/cm². Thereby, a light beam that had changed to polarized light afterpassing through the polarizing element was radiated on the photoreactivematerial film, and thus an anisotropic film was formed on the polarizingelement.

EXAMPLE 4

100 weight parts of polymethylpentene and 3 weight parts of needletitanium oxide were kneaded biaxially, from which a film 300 μm inthickness was prepared at 270° C. by a T-die, and the film was stretched6 times its original length at 190° C. In the thus stretched film, theneedle titanium oxide was aligned in a substantially certain direction.An anisotropic film was formed on a polarizing element in the samemanner as Example 1 except that the stretched film was used for thepolarizing element.

EXAMPLE 5

A mixture of a liquid crystalline compound (68.0 wt %, trade name:LCPCB483 manufactured by Vantico Co., Ltd.), a photoreactive material(29.2 wt %, trade name: LPPF301 manufactured by Vantico Co., Ltd.), aphotoinitiator (1.4 wt %, trade name: Irgacure369 manufactured by CibaSpecialty Chemicals) and an inhibitor (butyl hydroxytoluene, 1.4 wt %)was prepared. This mixture was dissolved in cyclopentanone to be 5 wt %,stirred at 50° C. for 30 minutes, and subsequently passed through a0.2-micron filter so as to prepare a coating solution. An anisotropicfilm was formed on a polarizing element in the same manner as Example 1except that this solution was used.

COMPARATIVE EXAMPLE 1

A film was laminated on a polarizing element in the same manner asExample 1 except that the photoreactive material was replaced bypolyvinyl alcohol.

COMPARATIVE EXAMPLE 2

A film was laminated on a polarizer in the same manner as Example 5except that the photoreactive material was not added.

For the anisotropic films obtained in Examples 1-5, the anisotropieswere evaluated in the following manner. Similarly, the films obtained inComparative Examples 1 and 2 were evaluated.

Evaluation (1) for Anisotropic Film

A compound exhibiting a cholesteric liquid crystalline phase (a mixtureof Paliocolor LC242 (trade name) and LC756 (trade name) manufactured byBASF) was dissolved in a cyclopentanone solvent at a rate of 20 wt %.This solution was applied by spin coating on a surface of an anisotropicfilm obtained in each Example. The thus coated film (a compound layer)was heated at 90° C. for 1 minute so as to align the compound exhibitinga cholesteric liquid crystalline phase, and then the compound waspolymerized through light irradiation so as to fix the alignment, andthus a layer 1 μm in thickness (a layer exhibiting a cholestericstructure) was formed. Table 1 below indicates whether this layer has aselective reflection wavelength or not. In Table 1, ‘Yes’ in each of theleft columns denotes that a selective reflection wavelength is observedand ‘No’ denotes that the selective reflection wavelength is notobserved.

As shown in Table 1, the layers formed on the anisotropic films ofExamples 1-4 exhibited selective reflection wavelengths. This shows thatthe anisotropic films of Examples 1-4 exhibited liquid crystal alignmentpower. On the other hand, since such a selective reflection was notobserved for the film of Comparative Example 1, it is confirmed that thefilm formed on a polarizer did not exhibit a liquid crystal alignmentpower.

Evaluation of Anisotropic Film (2)

A compound exhibiting a nematic liquid crystalline phase (trade name:Paliocolor LC242 manufactured by BASF) was dissolved in a cyclopentanonesolvent to make a 20 wt % solution, and this solution was applied byspin coating onto a surface of the anisotropic film obtained in anExample. Then, the thus coated film (compound layer) was heated at 90°C. for 1 minute so as to align the compound exhibiting the nematicliquid crystalline phase, and further the compound was polymerized bylight irradiation so as to fix the alignment, thereby forming a layer 1μm in thickness (a layer exhibiting a nematic structure).

Furthermore, the thus formed layer was transferred onto a transparentbase (a glass plate or a TAC film). For the layer on the transparentbase, the slow axis was measured by using a spectroscopic ellipsometer(trade name: M220 manufactured by JASCO Corporation). It was confirmedthrough the measurement that the polarization-transmission axisdirection of the polarizer used in the Examples and either a slow axisor fast axis of each layer are equal to each other. On the other hand,the nematic liquid crystal was not aligned in the film of ComparativeExample 1, but it became whitish to hinder detection of the axial angle.Similarly, the film of Comparative Example 2 became whitish to hinderdetection of the axial angle.

The anisotropic film side of the film obtained in Example 5 was bondedto the transparent base (TAC film) with an adhesive and then thepolarizer was peeled off to transfer the anisotropic film onto thetransparent base. Then, the phase difference and the slow axis of theanisotropic film were measured with a spectroscopic ellipsometer (tradename: M220 manufactured by JASCO Corporation). It was confirmed throughthe measurement that the polarization-transmission axis direction of thepolarizer used in Example 5 and a slow axis of the anisotropic film wereequal to each other. The retardation value was about 100 nm (measurementwavelength was 590 nm). This result shows that the anisotropic filmobtained in Example 5 exhibits an optical anisotropy. TABLE 1 UniaxialSelective reflection alignment of Relative angle between of cholestericliquid nematic liquid polarization transmission axis Retardation valuecrystal phase crystal phase and slow phase axis (degrees) (nm) Example 1Yes Good 90 — Example 2 Yes Good 90 — Example 3 Yes Good 0 — Example 4Yes Good 90 — Example 5 — — 0 100 Com. Ex. 1 No Poor Undetectable — Com.Ex. 2 — — Undetectable Undetectable

It was confirmed from Table 1 that the anisotropic films of Examples 1-4have liquid crystalline alignment power, the anisotropic film of Example5 exhibits optical anisotropy and all the anisotropic films in theExamples have excellent axial accuracy.

INDUSTRIAL APPLICABILITY

As mentioned above, according to the production method of the presentinvention, for example, an anisotropic film with excellent axialaccuracy can be produced easily, where either a special device forpolarized light irradiation or an advanced alignment adjustment is notrequired.

1. A method for producing an anisotropic film, the method comprising:disposing a film containing a photoreactive material on a polarizingelement; irradiating the film containing the photoreactive material withlight, through the polarizing element so as to provide an anisotropy tothe film containing the photoreactive material.
 2. The production methodaccording to claim 1, wherein the film containing the photoreactivematerial is formed by coating on the polarizing element a solution or amelt of a photoreactive material and by solidifying the solution or themelt.
 3. The production method according to claim 1, wherein thephotoreactive material has reactivity to light having a wavelength in arange of 1 nm to 780 nm.
 4. The production method according to any claim1, wherein the wavelength of the radiated light is in a range of 200 nmto 400 nm.
 5. The production method according to claim 1, wherein thewavelength of the radiated light is in a range of 290 nm to 400 nm. 6.The production method according to claim 1, wherein the wavelength ofthe radiated light is 310 nm.
 7. The production method according toclaim 1, wherein the polarizing element is at least one element selectedfrom the group consisting of a prism polarizer, a polarizing filter anda polarizer.
 8. The production method according to claim 1, wherein thefilm containing the photoreactive material is formed directly on thepolarizing element.
 9. The production method according to claim 1,wherein the film containing the photoreactive material is formed on thepolarizing element with interposition of a protective layer.
 10. Theproduction method according to claim 1, wherein the film containing thephotoreactive material further contains a liquid crystalline compound.11. The production method according to claim 10, wherein the liquidcrystalline compound is at least one liquid crystalline compoundselected from the group consisting of a liquid crystalline monomer, aliquid crystalline oligomer and a liquid crystalline polymer.
 12. Theproduction method according to claim 1, wherein the film containing thephotoreactive material further contains a non-liquid crystallinepolymer.
 13. The production method according to claim 1, wherein thephotoreactive material is at least one material selected from the groupconsisting of a liquid crystalline monomer having a photoreactive site,a liquid crystalline oligomer having a photoreactive site, and a liquidcrystalline polymer having a photoreactive site.
 14. An anisotropic filmproduced by the production method according to claim
 1. 15. Theanisotropic film according to claim 14, which comprises a liquidcrystalline alignment film.
 16. The anisotropic film according to claim14, which comprises an optically anisotropic film.
 17. An optical filmcomprising the anisotropic film according to claim
 14. 18. A liquidcrystal panel comprising a liquid crystal cell and an optical filmarranged on at least one surface of the liquid crystal cell, wherein theoptical film is the optical film according to claim
 17. 19. A liquidcrystal display comprising a liquid crystal panel, wherein the liquidcrystal panel is the liquid crystal panel according to claim
 18. 20. Animage display device comprising the optical film according to claim 17.